1. Field of the Invention
The present invention relates generally to an amplifier that has a power supply voltage source, the output voltage of which is modulated in accordance with the signal being amplified by the amplifier.
2. Description of the Prior Art
It is customary in amplifiers, particularly single-ended, push-pull amplifiers, to supply a fixed direct voltage. In the case of single-ended, push-pull amplifiers, the direct voltage power supply terminals may include a negative voltage terminal below the ground, or reference, voltage and a positive terminal above the reference voltage. The signal being amplified normally swings back and forth about the zero, or reference, point. As a result, in single-ended, push-pull amplifiers, current flows through the amplifying components, usually transistors of opposite conductivity type, when the voltage across the respective one of those transistors is high and that transistor is conductive. As a result, there is considerable loss of power and the efficiency of the amplifier circuit is relatively low.